In a Group III nitride compound semiconductor light-emitting device such as a blue light-emitting diode etc., various proposals have been made to obtain uniform light emission from the whole surface of the device.
For example, a light-transmissive electrode is stuck to a p-type layer so that an electric current can be injected into a wide range of a surface of the p-type layer. On this occasion, the light-transmissive electrode is formed as follows. A second electrode layer (e.g., Au) is laminated on a first electrode layer (e.g., Co) to form a light-transmissive electrode-forming layer. The light-transmissive electrode-forming layer is heat-treated in an oxygen-containing gas at a temperature of 500° C. to 600° C. As a result, the light-transmissive electrode-forming layer and the p-type layer are alloyed so that ohmic contact is ensured between the two layers. Incidentally, the distribution of constituent elements of the first electrode layer changes on this occasion.
According to the present inventors' examination, when heat treatment is performed in an oxygen-containing atmosphere at a high temperature of not lower than 500° C., a surface state of a p-seat electrode changes so that reliability of adhesive force to an electrically conductive wire is lowered.
Like the light-transmissive electrode, the p-seat electrode is formed by lamination of a plurality of electrode layers (e.g., successive lamination of Cr and Au viewed from the lower side). When heat treatment is carried out in an oxygen-containing atmosphere at a high temperature, the case where part of the lower metal layer moves to a surface and is segregated there may occur. In this case, there is the possibility that error may occur in image processing (for recognizing the p-seat electrode) at the time of wire-bonding in addition to lowering of adhesive force to the electrically conductive wire.